A variety of correction compositions have been commercially-available over the years. Such compositions comprise a masking pigment such as titanium dioxide, a resinous binder material such as ethyl cellulose and a volatile organic solvent for the binder material such as benzene, ethyl acetate, ethanol, trichlorethylene, or the like.
Such compositions have one or more disadvantages which render them unsafe and/or unsatisfactory for their intended function. The low boiling point hydrocarbons, ketones, esters and alcohols are flammable and represent a danger when used in the presence of an open flame such as a match lit by a typist. Moreover, such volatile solvents have rapid evaporation rates so that they evaporate from the applicator brush and from the mouth of the bottle during use, causing caking of the composition on the brush, narrowing of the inner neck of the bottle and the deposit of particles of solidified resin in the composition, which particles form an uneven masking coating over the images being covered during the subsequent use.
The use of less volatile solvents such as higher-boiling point hydrocarbons, including toluene and xylene, and certain chlorinated hydrocarbons, such as perchlorethylene, overcomes the problems of premature drying, caking, etc., and provides correction compositions which have a good levelling power, i.e., ability to form a smooth, even deposit over the image being masked prior to the evaporation of the solvent. However, such hydrocarbons are also flammable and their evaporation rate is so slow, under ambient conditions, that the typist must wait an undue length of time for the composition to dry and solidify prior to the typing of the correct image thereover, with resultant loss of time and efficiency.
Certain other solvents, such as trichlorethylene, have a satisfactory evaporation rate providing good levelling properties and rapid drying time but are dangerous to use because their vapours are dangerous to health, i.e., carcinogenic at the 100 ppm level, and it is possible to build up this concentration in an office having poor ventilation.